Lab 1 Flashcards
Bacteria have a cell wall that lies outside
their plasma membrane
Most bacteria have one of two kinds of cell wall
Gram-positive gram-negative
Both Gram-positive and gram-negative have a layer of protein and carbohydrate mesh called
Peptidoglycan
Peptidoglycan
Layer of protein and carbohydrate mesh
Cells with thick peptidoglycan
Gram-positive
Cells with thin peptidoglycan
Gram-negative cells
Also have an outer membrane outside their peptidoglycan
Gram-negative cells
Outer membrane of gram-negative cells consists of
A lipid bilayer with embedded proteins and other macromolecules
Simple staining
uses only one dye (also called a stain).
Dyes
are organic molecules with distinct coloration.
The most commonly used dyes are
basic dyes
Basic dyes
mildly basic on the pH scale and are positively charged.
Acidic dyes
negatively charged and are slightly acidic on the pH scale.
a basic dye will stain the
cells directly and an acidic dye will stain the background.
an acidic dye will stain
the background.
basic dyes include
malachite green, crystal violet, and safranin
Most stains used in microbiology are
basic
Colorful portions of the dyes are negatively charged
Acidic dyes
Colorful portions of the dyes are positively charged
Basic Dyes
Are repelled by microbial cells
Acidic dyes
Examples include nigrosin and India ink
Acidic dyes
Staining cells with a basic dye helps to determine cellular
morphology
Morphology
Morphology includes the physical traits of the organism such as its
Size
Shape
Arrangement
diplo
pairs
Palisades
fence like structure of rods
How do you make a simple stain?
- Make a smear
- Air-dry the smear
- Heat-fix the smear
- Stain the cells
